Colostrum is a thick, yellow fluid produced by mammary glands during the first few days after birth. It provides life-supporting immune (gamma globulin) and growth factors that ensure the health and vitality of a newborn.
The identities and functions of many of the bioactive principles of colostrum milk remain to be elucidated. However, colostrum is known to be a source of numerous bioactive hormones and growth factors, many of which have been demonstrated to influence intestinal growth, cell differentiation, and the development of the immune and enteroendocrine systems when administered in isolation.
Growth factors may be defined as proteins of 5 to 680 kDa that possess growth modulating bioactivities. Their biological actions also include the modulation and facilitation of the expression of cellular phenotype. To exert biological effects, growth factors must interact with specific high-affinity membrane receptors that activate appropriate signal transduction/second messenger cascades.
In their natural state, most growth factors are inert on human cells and have very high molecular weights (340-580 kDa). In order to become active, these growth factors need to be released from their inactive original forms either through hydrolysis or temperature change, or both.
Interestingly, even growth factors from non-human origin, such as those derived from porcine or bovine colostrum, when converted into their active forms, have been found to be active on human cells. This can be explained by the fact that the active forms of smaller molecular weight are almost completely homologous to the corresponding human growth factors. This has been found to be the case, for example, for the following families of factors: IGFs (1-3), TFGs β (1-3), PDGFs (AA, AB, BB), BMPs (1-24) and FGFs (1-16). These factors, when in active form, are recognized for their ability to proliferate and/or differentiate the stem cells of a newborn.
U.S. Pat. No. 6,277,813 (Kelly) describes the extraction of a novel growth factor from porcine colostrum. The process for extracting this growth factor, identified as CDGF for “Colostrum Derived Growth Factor”, includes the following steps: (1) separating all components of colostrum having a molecular weight below 200 kDa and discarding all components having a lower molecular weight; (2) treating the product of step 1 with dithiothreitol and boiling for 10 minutes; and (3) centrifuging the mixture of step (2) to spin down any precipitated matter and recovering the CDGF located in the supernatant.
U.S. Pat. No. 5,500,229 (Aalto et al.) discloses a colostral fraction having a low endotoxin, protein and immunoglobulin concentration. The colostral fraction is obtained through ultrafiltration of defatted colostrum using a membrane having a molecular weight cut off of 100 kDa and is intended for use as a supplement in cell culture media. The colostral fraction is said to be extremely useful either alone or when complemented by other supplements for replacing partially or completely fetal bovine serum in widely used cell culture media. The patent describes the effectiveness of the colostral fraction in the cultivation of hybridoma cells. (This invention is also described in Appl Microbiol Biotechnol (1992) 37: 451-456.)
European Patent No. 918464 (Adler et al.) discloses a process for preparing a colostral milk product from which casein has been largely removed and the colostrum has been defatted. The defatted and largely decaseinated colostrum is passed through an ultrafiltration column with an exclusion molecular mass of approximately 106. The product obtained can be further filtered using columns with exclusion molecular masses of 300 kDa and/or 150 kDa and/or 50 kDa and/or 30 kDa and/or 20 kDa and/or 10 kDa and/or 5 kDa and/or 1 kDa and/or 0.5 kDa. The resulting products are said to be suitable for use as an additive for drugs, food supplements, beverages, baby food, animal food, beverages in intensive sport for muscle protection or for reducing the muscular recovery phase, and for the prevention and treatment of bacterial, viral and mycotic infections.
Chinese Patent No. 1557837 (Gao Chunping) describes a process to separate insulin-like growth factor, immunoglobulins and casein from bovine colostrum. Colostrum is defatted and acidified to separate the insulin-like growth factor from binding, and the insulin-like growth factor is isolated through ultrafiltration, concentrated and freeze dried to obtain a powder. Immunoglobulins are separated through ultrafiltration and concentrated to prepare a powdered product. Casein is obtained through ultrafiltration or pH regulation, heat solidified and reacted with hydrolase to prepare casein phosphate polypeptide. The process is said to greatly lower production costs.
Chinese Patent No. 1557340 (also to Gao Chunping) describes a method of preparing a high bioreactivity growth factor and immunoglobulin from bovine colostrum. The method involves collecting colostrum 72 hours after parturition, defatting the colostrum through centrifugation, acidifying the solution, heating to solidify casein, centrifugally filtering or filtering the solution with cloth to eliminate casein, diluting the resulting solution, collecting the supernatant, concentrating with low molecular weight ultrafiltration membranes, and processing further in order to produce a dry powder preparation, a spray preparation, and the like. The product is intended for use in the treatment of various bacterial and viral infections.
U.S. Pat. No. 6,875,459 (Kopf et al.) discloses a method and apparatus for separation of milk, colostrum and whey components. In a preferred embodiment, the apparatus and method employ cross-flow filtration, chromatography and fermentation to separate the components of milk, colostrum and whey. The apparatus and method allow the extraction of immunoglobulins, among other factors.
European Patent No. 711171 (Laato et al.) describes a method for the improvement of wound healing in mammals, including humans, by using a colostral fraction. The colostral fraction is prepared by subjecting colostrum, from which part of the fat and cellular debris have been removed by conventional methods such as centrifugation, to ultrafiltration by using a membrane having a cutoff of 100 kDa and recovering the filtrate. The method for promoting wound healing consists of administering the colostral fraction locally.
PCT Publication No. WO 9811910 describes the use of a composition containing at least one compound with Growth Factor-like activity for the prevention or treatment of a gastrointestinal condition that is characterized at least partially by damage to epithelial cells and caused by the administration of a non-steroidal anti-inflammatory drug. Compositions for use in the invention may contain an IGF (e.g. IGF-1 or 2), a transforming growth factor (e.g. TGF1, TGF2 or TGF3), a keratinocyte growth factor, a fibroblast growth factor and/or a platelet-derived growth factor. The compositions containing the TGFs are preferably, though not exclusively, derived from colostrum. Similarly, PCT Publication No. WO 9811904 describes the use of colostrum or a derivative thereof for the prevention or treatment of a gastrointestinal condition that is characterized at least partially by damage to epithelial cells and caused by the administration of a non-steroidal anti-inflammatory drug. Derivatives suitable for use include ultrafiltered or microfiltered fractions of colostral whey (colostrum from which casein proteins have been removed), which are said to contain more concentrated Growth Factors relative to remaining colostral proteins and nutrients. Colostral whey may be used in liquid form (which may be defatted if desired) or may be further treated (such as being spray dried).
Other methods for the extraction of growth factors are known in the art, but surprisingly, no process appear to exist for deliberately and simultaneously isolating growth factors with highly disparate molecular weights. In addition, a number of methods rely on temperature conditions that have the effect of destroying the activity of the growth factors that are sought to be extracted.
There is therefore a need for a method of isolating growth and differentiating factors from colostrum that permits the separation of a great number of these factors (or “pools” of factors) in a manner that is efficient, reproducible and non-deleterious to their activities.